feat: add native agent with conversation history

src/backends/native/agent.ts

@@ -0,0 +1,38 @@
+import type { ModelClient, Message } from '../../models/types.js';
+
+export interface NativeAgentConfig {
+  modelClient: ModelClient;
+  systemPrompt: string;
+}
+
+export class NativeAgent {
+  private modelClient: ModelClient;
+  private systemPrompt: string;
+  private history: Message[] = [];
+
+  constructor(config: NativeAgentConfig) {
+    this.modelClient = config.modelClient;
+    this.systemPrompt = config.systemPrompt;
+  }
+
+  async process(userMessage: string): Promise<string> {
+    this.history.push({ role: 'user', content: userMessage });
+
+    const response = await this.modelClient.chat({
+      messages: [...this.history],
+      system: this.systemPrompt,
+    });
+
+    this.history.push({ role: 'assistant', content: response.content });
+
+    return response.content;
+  }
+
+  reset(): void {
+    this.history = [];
+  }
+
+  getHistory(): Message[] {
+    return [...this.history];
+  }
+}